Lamp base



FIG. 1 is a top, front perspective view of a lamp base showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a rear elevational view thereof;

FIG. 4 is a side elevational view thereof, the opposite side being identical;

FIG. 5 is a top plan view thereof;

FIG. 6 is a bottom plan view thereof. 

The ornamental design for lamp base, as shown. 